Earth and Space Science TEK 10 F

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Earth and Space Science TEK 10 F
(10)  Solid Earth. The student knows that plate
tectonics is the global mechanism for major
geologic processes and that heat transfer,
governed by the principles of thermodynamics, is
the driving force. The student is expected to
(f)  evaluate the role of plate tectonics with
respect to long-term global changes in Earth's
subsystems such as continental buildup,
glaciation, sea level fluctuations, mass
extinctions, and climate change.
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Plate Tectonics Role in
Continental Buildup
Continental buildup is simply the accretionary
process that helps continents to evolve. One need
only look to the Wilson Cycle to see how
continents evolve over time, from simple to
complex.
To the aged, and dying
From the very, very young
Without plate tectonics, the continents would
only decline through weathering and erosion.
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Plate Tectonics Role in
Glaciation
Tectonics dictate climate, and the key to
glaciation is climate. Glaciers atop mountains
in temperate (lower) latitudes flow downhill,
scouring away the surface of the mountain. Over
millennia, such erosion can reduce the height and
width of a mountain range by miles. However in
very cold climates (and higher latitudes) such as
the Patagonian Andes, rather than scraping away
the surface of the mountain, glaciers protect the
mountain top and sides from erosion.
As glaciers move, they push about great amounts
of debris. When continents are glaciated, they
ride lower in the asthenosphere because of
increased mass.
Tectonics dictates latitude and altitude of
places on Earth.
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Plate Tectonics Role in
Sea Level Fluctuations
At times during Earth's long history, the
configuration of the continents and seafloor have
changed due to plate tectonics. This affects
global sea level by determining the depths of the
ocean basins.
The depth of the ocean basins is all about the
age of oceanic lithosphere as lithosphere
becomes older, it becomes denser and sinks. The
older the oceanic lithosphere, the deeper the
ocean basin, the LOWER the sea level. The younger
the oceanic lithosphere, the shallower the ocean
basin, the HIGHER the sea level.
The older basin is on the left side. On which
side would the sea level be higher? Right!
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Eustatic vs. Isostatic Changes
The term "isostatic" refers to changes in the
level of the land relative to a fixed point in
the Earth, possibly due to thermal expansion or
tectonic effects it implies no change in the
volume of water in the oceans. As glaciers melt,
the continental mass decreases, and the continent
may rebound. No increase in oceanic volume, but
sea-level appears to drop.
The term "eustatic" refers to global changes in
sea level relative to a fixed point, such as the
center of the Earth, which results in an actual
change in the VOLUME of the oceans. Eustatic
sea-level changes occur when the actual volume of
the oceans increases or decreases perhaps through
glaciation, or glacier melting.
Much of sea-level rise today is due to thermal
expansion. As sea water warms, it expands.
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When there were large amounts of continental
crust near the poles, the rock record shows
unusually low sea levels during ice ages, because
there was lots of polar land mass upon which snow
and ice could accumulate. Look at each of the
following images of Earth in geologic past, and
determine if sea-levels would be low, or
highrelatively.
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Plate Tectonics Role in
Mass Extinctions

• Movement of the continents into some
  configurations can cause or contribute to
  extinctions in several ways.
• initiating or ending ice ages
• changing ocean and wind currents and thus
  altering climate
• opening seaways or land bridges which expose
  previously isolated species to competition for
  which they are poorly adapted
• Occasionally continental drift creates a
  super-continent which includes the vast majority
  of Earth's land area, which in addition to the
  effects listed above is likely to reduce the
  total area of continental shelf (the most
  species-rich part of the ocean) and produce a
  vast, arid continental interior which may have
  extreme seasonal variations.
• It is widely thought that the creation of the
  super-continent Pangaea contributed to the
  End-Permian mass extinction

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Plate Tectonics Role in
Climate Change
The distribution, elevation, and areal extent of
the continents each influence climate. In
addition, plate tectonics influences climate
by modifying the atmospheric concentration of
carbon dioxide.

• Five major factors must be addressed
• differences in surface albedo
• land area at high latitudes
• transfer of latent heat
• restrictions on ocean currents
• thermal inertia of continents and oceans.

Considering that the amount of incoming solar
energy is very different at different latitudes,
the latitudinal distribution of land and sea has
a strong potential to influence the total energy
budget of Earth.
Land at high latitudes provides a surface for the
accumulation of snow and year-round ice. Snow and
ice have a very high albedo for fresh snow it
approaches .65 to .80. Consequently,
high-latitude land area, if snow-covered, can
also dramatically influence the Earths energy
budget.
The largest energy fluxes at the surface of Earth
involve moisture (latent heat flux). Clearly, the
distribution of land and sea will influence
evaporation and precipitation and therefore the
total energy budget of the atmosphere.
The distribution of land can block poleward heat
transport by the ocean and may influence polar
climates and the subsequent extent of ice and
snow cover. Thus, the shape and size of the ocean
basins become a factor in controlling global
climate.
A continental surface has little thermal inertia.
Basically, a continental surface responds rapidly
to the current solar input. In contrast, the
oceans have a large heat capacity. Therefore, the
thermal inertia of the oceans tends to moderate
the role of the seasonal cycle of insolation.